The contribution of beef production to global warming is frequently noted as one of the worst foods, particularly because they produce methane as part of their digestion. Cheese is less frequently discussed in this manner, despite also being produced from cows, presumably with the production of methane at similar amounts. From wikipedia it would appear that the food conversion ratio of dairy cattle is about the same as that of beef cattle*, therefore the principal inputs are the same.
I can see 2 interpretations of this; either cheese is about the same impact as beef, or that the 2 industries are so tightly bound ** that it is distinguishing their impacts is impossible, therefore it is principally a question of how much money you spend on each of these products as to the environmental impact.
Can anyone critique my reasoning? Is is possible to determine the relative or absolute impacts of these 2 foodstuffs?
* Food conversion ratio (FCR) is the ratio of food eaten to food produced. I would expect this to capture the primary environmental cost of a foodstuff produced by a cow.
Beef: an FCR calculated on live weight gain of 4.5–7.5 was in the normal range with an FCR above 6 being typical. Most cattle will have an average dressing percentage of 63 percent.
Dairy: Using an FCR calculated just on the weight of protein and fat, as of 2011 an FCR of 13 was poor, and an FCR of 8 was very good. Lactose accounts for ~30% for the caloric value of whole milk.
Therefore the calculation is:
FCR of dairy = 13/1.3 to 8/1.3 = 10 to 6.2
FCR of beef = 4.5/0.63 to 7.5/0.63 = 10.3 to 7.1
Close enough to be roughly the same.
** You cannot produce milk without producing calves, and these calves make up a large part of the global beef herd.